The present invention relates to the production of composite fasteners and is particularly concerned with the production of composite blind self-sealing fasteners for use on composite and metallic structures, such as integral fuel tank structures for aircraft.
Structural components particularly advantageous for aircraft and other vehicles, e.g., in the form of beams, ribs and other structural components, such as are emploved in the construction of aircraft fuel tanks, are often made of lightweight material relative to their strength and stiffness. Such materials are composite materials, which, as is well-known in the art, are comprised of fibers of various types, such as graphite fibers in cloth and/or tape orientations, impreonated with a binder material, usually a plastic, such as an epoxy resin.
Fasteners heretofore oenerally employed in conjunction with such composite structural components have been metallic fasteners. However, the use of such metallic fasteners on composite structures has the disadvantage that the metallic fasteners are incompatible with composite structures due to the difference in thermal expansion of the metallic components in relation to composite structural components, resulting in insecure or loose connections, or leakage in the case of fuel tank structures, especially as a result of substantial temperature variations, e.g., during operation of an aircraft.
Adhesively securable fasteners are known, for example, as described in U.S. Pat. No. 4,425,065. The patent discloses a fastener wherein an adhesive forms an external bulb to hold the fastener in position. Examples of other adhesively secured fasteners include U.S. Pat. Nos. 4,100,954; 4,102,030; 4,419,805; and 4,514,125. However, these prior art adhesively securable fasteners are relatively complex and expensive and/or have other disadvantages, which have heretofore rendered them unsuitable for use as fasteners on composite structures, particularly for use as sealing fasteners on aircraft fuel tank composite structures.
It is an object of the present invention to provide an improved composite self-sealing fastener.
Another object of the invention is the provision of composite self-sealing blind fasteners for use with composite structural components, particularly the composite components of fuel tank structures employed in aircraft.
A still further object is to provide a self-sealing composite blind fastener of the above type employing curable resin sealants, for use with composite structural components, and which is of relatively simple construction, readily operable and dependable, and which can be used in the field, e.g., for battle repair damage.